Ionization-type fire or smoke sensing system
USRE30117E · kind E · reissue
Assignee
Inventors
Key dates
| Filing date | Feb 13, 1978 |
| Grant date | Oct 16, 1979 |
| Priority date | — |
| Expiry date | Feb 13, 1998 |
Classification
- Technology area (CPC —)General
Abstract
To render an ionization-type sensing element essentially immune to changes in ambient conditions, principally temperature or operating voltage, while still using low-current draining circuits to sense response of the ionization chamber of the sensor, the threshold response level of a field effect transistor (FET) is arranged to have approximately the same temperature response characteristic, within the range of ambient temperature considered, as the ionization cell so that the overall circuit or system combination of the cell and FET amplifier will have a response which is essentially independent of ambient temperature or similar conditions. The source path of the FET is connected to a voltage divider which is so dimensioned that the voltage division ratio (R.sub.2 /R.sub.1) is related to the temperature coefficient (.alpha.) of the base-emitter voltage of the FET and the temperature coefficient (.beta.) of the measuring ionization cell chamber: EQU R.sub.2 /R.sub.1 =(.beta./.alpha.)-1.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.